The period calculator estimates when your next period may start from the first day of your last period and cycle length, listing three upcoming reference dates—not for contraception or diagnosis.
How to use
- Enter last period start date.
- Enter cycle length (often 21–40 days).
- Read the next three dates on the timeline.
For ovulation and fertile days, use the ovulation calculator.
More tools on the health hub. For planning reference only—not medical, nutrition, or obstetric advice.
Frequently asked questions
When is my next period?
Enter last period start and cycle length (days between starts, often 21–40) for the next three reference dates—irregular cycles reduce accuracy.
Unknown cycle length?
Try 28 days, then adjust from 3–6 months of logs. Very short, long, or erratic cycles → see a clinician.
Can I use this for contraception?
No. Calendar methods are unreliable for contraception. Use approved contraception; for TTC see the ovulation calculator plus tests.
Vs ovulation calculator?
The ovulation tool estimates fertile days; this page estimates period starts.
Is this medical advice?
No—results are for planning reference only. See clinicians for pregnancy, pediatrics, cycle disorders, or sleep conditions. Do not rely on calendar math alone for contraception.